=«il  ' 


No.  195G 


DESCRIPTION  OF 

2-INCH 
TELESCOPIC  SIGHTS 


MODEL  OF  1906 


(5  PLATES) 


OCTOBER  n, 
REVISED  OCTOBER  U,  I9I0 
REVISED  DECEMBER  16,  I9I3 
REVISED  MARCH  J,  I9I7 


WASHINGTON 

GOVERNMENT  PRINTING  OFFICE 

1917 


No.  1 966 


DESCRIPTION  OF 

2-INCH 
TELESCOPIC  SIGHTS 

MODEL  OF  1906 


(5  PLATES) 


OCTOBER  n,  1907 
REVISED  OCTOBER  11,  19 10 
REVISED  DECEMBER  16,  I9J3 
REVISED  MARCH  I,  191 7 


WASHINGTON 

GOVERNMENT  BRINTING  OFFICE 

1917 


^S^^^' 

^^i 

^    .T 
\ll' 


1 


War  Department, 
Office  of  the  Chief  of  Ordnance, 

Washington,  March  1,  1917. 
This  manual  is  published  for  the  information  and  government  of  the  Regular 
Army  and  National  Guard  of  the  United  States. 
By  order  of  the  Secretary  of  War: 

William  Crozier, 
Brigadier  General,  Chief  of  Ordnance, 

(3) 


362109 


Digitized  by  the  Internet  Archive 

in  2007  with  funding  from 

Microsoft  Corporation 


http://www.archive.org/details/descriptionof2in00unitrich 


TABLE  OF  CONTENTS. 


Description 7-9 

Principal  parts 9 

Telescope 9-10 

Adjustment 11-12 

Care  and  preservation 12-13 

Dismantling  and  assembling 13 

Nomenclature 14-17 

(5) 


TWO-INCH  TELESCOPIC   SIGHTS, 

MODEL  OF  1906. 

(three  plates.) 


(The  Telescopes  o'p  these  Sights  were  Designed  by  the  Warner  &  Swasey 

Co.,  Cleveland,  Ohio.) 

[IMPORTANT  CHANGES  IN  THIS  PAMPHLET  ARE  SHOWN  IN  BOLD  FACE  TYPE. 


1.  The  advantages  gained  by  the  use  of  a  telescope  in  laying  a  piece 
consist  of  a  decrease  in  personal  error  and  an  increase  in  power  of 
vision.  By  using  a  telescopic*sight  a  gunner  is  enabled  to  see  clearly 
an  object  which  is  indistinct  to  the  naked  eye,  and  to  lay  a  gun  on  it 
with  facility  and  accuracy. 

2.  For  the  designation  of  parts,  see  Plates  I,  11^  and  III,  and  the 
list  attached  hereto  giving  the  nomenclature  which  should  be  used 
when  ordering  sp^^re  parts.  The  sight  was  originally  designed  for 
use  on  the  left  side  of  15-pounder  barbette  carriage,  model  of  1903. 
Plates  I  and  II  show  this  sight.  Later,  it  was  desired  to  provide  an 
additional  sight  on  f.he  right  side  and,  where  necessary,  certain  parts 
were  made  '^ right  and  left."  Still  later,  however,  the  fu'st  sights 
were  removed  from  the  left  side,  leaving  only  right-hand  sights  now 
in  service.  The  15-pounder  barbette  carriages,  model  of  1903,  are 
the  only  carriages  equipped  with  this  model  sight. 

3.  The  principal  parts  are  the  telescope  (PI.  Ill),  the  front  and 
rear  sight  brackets  (24  and  25),  the  cradle  (15),  the  open  sights  (4 
and  17),  the  sight  shank  with  deflection  worm  box  and  head  of 
sight  shank  (23  and  8),  the  range  drum  (29),  the  gear-case  cover 
and  cover  for  range  drum  (30),  the  elevating  worm  (36),  the  ful- 
crum (20),  the  lighting  cables  (26),  the  deflection  scale  (38),  and  the 
elevating  worm-gear  shaft  (39). 

4.  The  front  and  rear  sight  brackets  (24  and  25)  are  bolted  to  the 
carriage  at  their  lower  ends.  The  cradle  (15)  is  assembled  at  the 
forward  end  to  the  front-sight  bracket  (24)  by  means  of  the  fulcrum 
(20).  The  fulcium  axes  have  bearings  in  the  two  sides  of  the  front- 
sight  bracket  (24),  permitting  rotation  for  elevation  and  depres- 
sion, and  the  fulcrum  (20)  has  a  short  vertical  shaft  on  its  under- 
side, to  which  the  forward  end  of  the  cradle  (15)  is  assembled,  so  as 
to  allow  rotation  in  azimuth  only.  At  the  rear  end  the  cradle  (15) 
is  assembled  to  the  sight  shank  (23)  by  means  of  the  sight-shank 

(7) 


head  and  the  deflection  worm  (40).  The  latter  is  seated  in  the  sight- 
shank  head  which  thus  forms  the  deflection  worm  box  (8)  and  meshes 
into  a  worm  segment  cut  in  the  cradle  (15).  The  front  and  rear 
faces  of  the  deflection  worm  box  (8)  and  the  head  of  the  sight  shank 
are  arcs  of  circles  having  their  common  center  on  the  axis  of  the 
verticle  shaft  of  the  fulcrum  (20).  The  front  and  rear  faces  of  the 
sight  shank  (23)  and  of  its  seat  between  the  rear  sight  bracket  (25) 
and  gear-case  cover  (30)  are  arcs  of  circles  having  their  common 
center  at  the  middle  point  of  the  central  line  of  the  fulcrum  axis. 
The  sight  shank  (23)  is  thus  assembled  between  the  rear  sight  bracket 
(25)  and  the  gear-case  cover  (30),  and  is  held  in  place  by  the  gear- 
case  cover  (30)  and  the  elevating  gearing. 

5.  The  elevation  of  the  sight  and  the  rotation  of  the  range  drum 
(29)  are  accomplished  by  the  elevating  gearing,  consisting  of  the 
elevating  worm  (36)  and  the  elevating  worm-gear  shaft  (39),  with 
its  worm  gear  and  spur  gear,  the  latter  two  being  on  one  piece, 
called  the  elevating  worm  gear  (2S4B).  The  elevating  worm  (36) 
engages  the  worm  gear  and  the  spur  engages  the  sight-shank  rack. 
The  piece  on  which  these  two  gears  are  cut  is  mounted  on  a  squared 
section  of  the  elevating  worm-gear  shaft  (39)  which  is  also  the 
range-drum  shaft,  the  range  drum  (29)  being  mounted  on  this  shaft 
and  held  in  place  by  the  friction  of  a  range-drtltn  washer  (56)  bear- 
ing against  the  range  drum  (29),  and  the  friction  of  the  range  drum 
(29)  on  a  shoulder  of  the  elevating  worm-gear  shaft  (39).  An  ele- 
vating gear  spring  (2S4M),  11  feet  long,  is  secured  at  one  end  to  the 
elevating  worm-gear  shaft  (39),  is  wound  several  times  around  the 
elevating  worm-gear  shaft  (39),  and  has  the  other  end  secured  to 
the  gear-case  cover  (30).  The  gear-case  cover  (30)  is  bolted  to  the 
rear  sight  bracket  (25).  By  rotating  the  elevating  worm  (36)  the 
elevating  worm-gear  shaft  (39)  is  moved,  adding  to  or  releasing  ten- 
sion on  the  elevating  gear  spring  (2S4M),  depressing  or  elevating 
the  cradle  (15)  by  means  of  the  sight  shank  (23),  and  rotating  the 
range  drum  (29).  The  elevating  gear  spring  (2S4M)  serves  to  equal- 
ize the  force  required  to  depress  or  elevate  the  cradle  (15).  The 
gear-case  cover  (30)  and  the  rear  sight  bracket  (25)  serve  to  protect 
the  elevating  gearing,  the  elevating  gear  spring  (2S4M),  and  the  range 
drum  (29).  The  range  pointer  (52)  is  attached  to  the  gear-case 
cover  (30).  The  range  drums  (29)  for  these  sights  will  not  be  used 
as  such  and  wiU  not  be  graduated. 

6.  The  elevation  scale  (33)  is  of  German  silver,  is  dovetailed  into 
the  rear  face  of  the  sight  shank  (23),  and  reads  from  zero  to  16°,  the 
least  reading  being  6'.  The  range  pointer  (52)  is  a  piece  of  German 
silver  dovetailed  into  the  gear-case  cover  (30)  just  opposite  the 
lamp  housing  for  range  drum  (29)  and  elevation  scale  (33). 


7.  Deflection  is  obtained  by  rotating  the  deflection  worm  (40), 
which  is  seated  in  the  deflection-worm  box  (8)  and  meshes  into  a 
worm  segment  cut  into  the  cradle  (15)  where  the  box  is  seated. 

8.  The  deflection  scale  (38),  of  German  silver,  is  dovetailed  into  the 
rear  end  of  the  cradle  (15).  The  numbers  on  the  scale  are  reference 
numbers,  '^3"  representing  the  origin  or  central  position  of  the 
deflection  scale  (38).  The  interval  between  whole  numbers  is  equal 
to  one  degree  of  arc.  The  least  reading  of  the  scale  is  0.10°,  or  6 
minutes  of  arc.  The  deflection  scale  pointer  (19)  is  cut  on  a  German- 
silver  plate  secured  to  a  lug  projecting  from  the  rear  of  the  sight 
shank  (23).  The  lamp  bracket  for  illuminating  the  deflection  scale 
(38)  and  deflection  scale  pointer  (19)  is  part  of  the  rear  end  of  the 
cradle  (15),  and  is  situated  immediately  above  the  deflection  scale  (38). 

9.  The  open  sight  consists  of  a  peep  sight  (4)  in  rear  and  of  a  front 
sight.  An  arm  of  the  peep  sight  extends  downward,  terminating  in  a 
foot  which  is  attached  to  the  4eft  side  rear  end  of  the  cradle  (15)  by 
two  peep  sight  screws  (55)  and  two  dowel  pins.  The  front  sight  is 
attached  to  the  front  sight  holder  (16),  mounted  at  the  forward  end, 
left  side  of  cradle  (15).  The  open  sight  is  for  use  in  locating  an  object 
quickly. 

10.  Each  sight  is  provided  with  two  small  electric  lamps  (EoJ)  or 
(E9H)  of  2  candlepower,  which  for  220-volt  circuits  are  74  volts  and 
0.147  amperes;  for  110-volt  circuits  106  to  116  volts  and  0.094  to 
0.103  amperes.  One  of  these  lamps  illuminates  the  cross  wires  (47) 
of  the  telescope,  giving  bright  lines  in  a  dark  field,  and  the  other  one 
illuminates  the  deflection  scale  (38).  They  are  connected  with  the 
electric  circuit  by  the  lighting  cables  (26)  and  plug  connections.  The 
lamp  that  illuminates  the  cross  wires  (47)  of  the  telescope  is  placed  in 
a  lamp  bracket  (11)  that  is  screwed  to  the  eye  end  of  the  telescope 
tube  (9)  on  the  right-hand  side.  Two  small  platinum  mirrors 
(EA17W)  deflect  the  rays  of  light  through  two  openings  cut  through 
the  telescope  tube  (9)  90°  apart.  These  openings  are  so  arranged 
that  the  light  from  each' mirror  is  thrown  upon  the  full  length  of  the 
cross  wire  (47)  opposite. 

11.  The  principal  parts  of  the  telescope  are  the  telescope  tube  (9), 
the  objective  (49),  the  Porro  erecting  prisms  (48  and  48),  the  draw 
tube  (50),  the  cross- wire  holder  (46),  the  focusing  sleeve  (44),  the 
focusing  ring  (3),  and  the  eyepiece  (1,  2,  42,  43,  and  45). 

12.  The  telescope  tube  (9)  is  the  principal  piece  to  which  the  other 
parts  are  assembled.  The  objective  (49)  is  double,  is  seated  in  an 
objective  cell  (EA17E)  that  screws  into  the  forward  end  of  the  tele- 
scope tube  (9),  and  gives  a  2-inch  clear  aperture.  The  Porro  erecting 
prisms  (48  and  48)  are  two  in  number,  secured  in  place  by  the  prism 
holder  (53).     There  are  no  cemented  surfaces,  thereby  reducing  the 

84531—17 2 


10 

chance    of   injury,    rendering    replacement    easier,    and    facilitating 
cleaning. 

13.  The  cross  wires  (47)  are  secured  to  the  cross-wire  holder  (46) 
by  four  clamps,  and  are  at  right  angles  to  each  other.  The  cross- 
wire  holder  (46)  is  secured  to  the  draw  tube  (9)  by  the  cross-wire 
holder  screws  (EA18E).  The  draw  tube  (9)  is  assembled  to  the 
focusing  sleeve  (44)  so  as  to  allow  longitudinal  motion  of  the  former 
when  the  focusing  ring  <3)  is  rotated,  and  to  force  rotation  of  the' 
draw  tube  (50)  when  the  focusing  sleeve  (44)  is  rotated.  The  focusing 
sleeve  (44)  is  screwed  into  the  rear  end  of  the  telescope  tube  (9)  and 
is  secured  by  a  set  screw  (EA18H).  The  focusing  ring  (3)  is  seated 
on  the  focusing  sleeve  (44)  by  a  threaded  surface,  its  motion  being 
limited  by  the  telescope  tube  (9)  in  front  and  the  focusing-sleeve  nut 
(37)  in  rear.  When  turned,  it  transmits  to  the  draw  tube  (50)  and 
cross-wire  holder  (46)  its  longitudinal  motion  only. 

14.  The  eyepiece  consists  of  the  eyepiece  tube  (43)  the  field  lens 
(45),  the  eye  lens  (42)  in  its  holder,  the  eye-lens  cell  (2S9B),  and  the 
rubber  hood  (1).  The  eyepiece  tube  (43)  is  screwed  into  the  draw 
tube  (50)  and  carries  the  field  lens  (45)  and  the  eye  lens  (42)  with  the 
eye-lens  cell  (2vS9B),  the  eyepiece  cover  (54)  being  screwed  to  the 
latter.  There  is  an  amber  glass  disk  (2S9D)  in  a  holder  (41)  that  is 
piloted  so  that  it  may  ])e  used  or  not,  as  desired.  This  shade  is 
provided  to  protect  the  eye  from  a  glare  of  light.  The  eyepiece 
serves  to  magnify  the  image  at  the  cross  wires  (47)  and  to  converge 
the  rays  of  light  into  a  pencil  of  a  size  suited  to  enter  the  pupil  of  the 
eye. 

15.  The  front  end  of  the  telescope  is  provided  with  a  movable 
objective  shutter  (13)  for  the  protection  of  the  objective  (49). 

16.  The  clear  aperture  of  the  telescope  is  2  inches,  the  focal  length 
is  12  inches,  the  magnifying  power  of  the  eyepiece  is  8,  with  a  field 
of  4J°.  A  rubber  hood  (1)  for  the  eyepiece  is  provided  for  the  pur- 
pose of  diminishing  shock  to  the  eye  or  face  upon  discharge  of  the  gun. 
The  rubber  hood  (1)  is  so  shaped  as  to  keep  out  light  from  the  sides 
and  rear. 

17.  The  image  is  erect,  the  erection  being  secured  by  the  Porro 
prisms  (48  and  48),  each  of  which  twice  totally  reflects  the  rays  of 
light  at  an  angle  of  90°,  so  that  the  rays  emerge  parallel  to  the 
entering  rays  and  in  the  original  direction.  The  paths  of  two  rays 
of  light  are  shown  on  Plate  III,  which  illustrates  the  erection  process. 

18.  The  telescope  is  secured  in  position  on  four  accurately  bored 
segmental  projections  on  the  cradle  (15)  by  the  front  and  rear  tele- 
scope clamps  (12  and  5)  each  of  which  is  machine  finished  to  proper 
bearing  on  the  upper  portion  of  the  telescope  to  secure  proper  align- 
ment of  the  optical  axis  and  to  insure  verticality  of  the  vertical  wire. 


11 

19.  The  front  and  rear  sight  brackets  (24  and  25)  are  bolted  to 
seats  provided  on  the  gun  cradle,  so  that  the  motion  of  the  sight 
cradle  (15)  must  conform  to  that  of  the  gun,  and  when  the  sight  is 
properly  assembled  to  the  carriage  and  the  elevation  and  deflection 
readings  are  zero  the  optical  axis  of  the  telescope  and  the  axis  of  the 
bore  of  the  gun  will  remain  parallel  at  all  elevations.  Therefore,  if 
the  sight  be  set  at  the  elevation  required  for  the  range  of  the  object 
to  be  fired  at  and  then  be  laid  upon  it,  the  gun  will  automatically 
receive  the  same  elevation.  Since  the  deflection  movement  of  the 
sight  is  independent  of  the  gun,  any  deflection  necessary  may  be 
given  without  affecting  the  elevation. 

20.  In  assembling  the  front  and  rear  sight  brackets  (24  and  25) 
great  care  should  be  taken  to  see  that  the  seats  on  the  gun  cradle 
have  been  properly  prepared  and  that  burrs,  paint,  and  rust  are 
removed  from  aU  bearing  surfaces.  A  small  obstruction  of  this 
kind  will  throw  the  sight  shank  (23)  out  of  plumb.  In  setting  up 
the  bolts  all  should  be  brought  to  a  firm  bearing  before  any  are  set 
up  tight. 

21.  Neither  the  elevation  nor  the  deflection  scale  pointer  (19)  is 
marked  by  the  manufacturer  of  the  sights,  since  there  is  no  adjust- 
ment for  either  on  the  carriage.  The  elevation  pointer  should  be 
cut  at  the  works  of  the  builders  of  the  carriage  to  allow  for  any 
possible  inaccuracy  in  the  seats,  and  the  deflection  scale  pointer  (19) 
should  be  put  on  at  the  emplacement  after  the  gun  is  mounted. 

22.  After  the  sight  has  been  assembled  to  the  carriage,  and  while 
the  gun  is  at  zero  elevation,  the  sight  should  be  accurately  leveled 
and  the  elevation  pointer  cut  exactly  opposite  the  zero  of  the  eleva- 
tion scale  (33). 

23.  The  position  of  the  deflection  scale  pointer  (19)  may  be  deter- 
mined by  adjusting  the  telescopic  sight  so  that  its  axis  intersects  the 
axis  of  the  gun  at  mid  range.  The  index  line  should  then  be  cut 
opposite  the  reference  number  3  on  the  deflection  scale  (38). 

ADJUSTMENT. 

24.  The  cross  wires  (47)  are  rendered  distinct  by  screwing  the 
eyepiece  in  or  out,  and  this  adjustment  has  no  other  object.  If 
the  telescope  is  frequently  used  by  one  observer,  the  eyepiece  can 
be  reset  at  the  correct  position  by  using  the  graduations  on  the  eye- 
piece cover  (54).  After  bringing  the  cross  wires  (47)  into  distinct 
vision  by  adjusting  the  eyepiece  the  image  may  be  brought  into  the 
plane  of  the  cross  wires  (47)  by  moving  the  focusing  ring  (3)  until 
the  object  appears  distinctly,  and  there  is  no  parallax;  that  is,  when 
the  object  does  not  seem  to  shift  relative  to  the  cross  wires  (47)  when 
the  eye  is  moved  from  side  to  side  of  the  eyepiece.  When  a  sight  is 
adjusted  by  the  removal  of  parallax  it  is  correct  for  aU  observers 


12 

for  a  given  range.  Adjustment  of  the  eyepiece  is  required  to  accom- 
modate variations  in  the  eyes  of  different  observers  but  is  not  required 
for  variations  in  range. 

25.  The  cross  wires  are  mounted  on  the  cross-wire  holder,  which  is 
held  in  position  by  four  adjusting  screws  which  pass  through  elongated 
holes  in  the  focusing  sleeve.  These  screws  may  be  reached  by  first 
removing  the  focusing  sleeve  nut  and  unscrewing  the  focusing  ring 
until  the  slotted  screws  can  be  seen  through  the  elongated  openings 
in  the  focusing  sleeve. 

26.  When  adjusting  the  cross  wires  the  coUimating  telescope  fur- 
nished with  the  optical  repair  kit  should  be  placed  in  the  proper 
rings  and  securely  clamped  in  the  sight  cradle,  and  when  properly 
adjusted  should  be  sighted  on  a  target  having  plumb  and  horizontal 
lines.  The  telescopic  sight  is  now  placed  in  the  cradle  with  its  axis 
coinciding  with  the  axis  of  the  collimating  telescope. 

27.  The  cross  wires  should  be  adjusted  by  means  of  the  adjusting 
screws  to  coincide  with  the  same  plumb  and  horizontal  lines  which 
were  seen  through  the  collimating  telescope. 

28.  The  slotted  holes  in  the  focusing  sleeve  permit  a  slight  rotary 
motion  of  the  cross-wire  holder  to  secure  vertical  and  horizontal 
alignment.  The  focusing  sleeve  should  always  be  screwed  into  the 
telescope  tube  and  locked  in  place  with  a  set  screw  (EA18H). 

29.  To  adjust  the  tension  of  the  elevating  gear  spring  (2S4M)  run 
the  sight  shank  (23)  out  of  mesh,  turn  the  elevating  wheel  (21)  to 
the  right  to  relieve  tension  or  to  the  left  to  increase  tension,  and 
reengage  the  rack.  When  the  cradle  (15)  and  telescope  are  in  place 
and  the  elevation  is  8°  the  force  required  to  rotate  the  elevating  wheel 
(21)  should  be  the  same  for  both  directions.  The  cradle  (15)  must 
be  disengaged  from  the  head  of  the  sight  shank  (23)  before  attempting 
this  adjustment. 

CARE  AND  PRESERVATION. 

30.  Telescopic  sights  are  necessarily  delicate  instruments,  and 
must  not  be  subjected  to  rough  usage,  jars,  or  strains.  When  not 
in  use,  the  telescope  should  be  kept  in  its  leather  case  and  should  be 
stored  in  a  dry  place.  It  should  be  occasionally  examined  to  insure 
its  not  being  corroded  by  tannic  acid  from  the  case.  All  traces  of 
dust  and  moisture  should  be  removed  before  putting  the  sight  in  the 
case. 

31.  To  obtain  satisfactory  vision,  the  glasses  should  be  kept  per- 
fectly clean  and  dry.  In  case  moisture  collects  on  the  glasses,  place 
the  telescope  in  a  gentle  warmth;  this  is  usuaUy  sufficient  to  remove 
it.  Material  issued  for  the  cleanhig  of  lenses  only  should  be  used, 
care  being  taken  that  the  cleaning  material  contains  no  dirt  or  grit. 
The  lenses  and  prisms  will  seldom  require  cleaning  on  the  inside, 


13 

but  when  necessary  they  should  be  removed  only  in  a  room  free  from, 
dust  and  moisture  and  hj  a  competent  person  who  has  material  for 
resealing  all  exterior  joints. 

32.  The  erecting  prisms  (48  and  48)  should  not  be  removed  except 
by  one  especially  trained  in  the  care  of  telescopes,  and  if  they  need 
repair  report  should  be  made  to  the  proper  authority.  Removal  is 
apt  to  disturb  the  adjustment,  and  finger  marks  or  lint  will  cause 
difficulty. 

33.  The  cross  wires  (47)  are  unprotected  when  the  eyepiece  is 
removed,  and  great  care  must  be  exercised  not  to  touch  them,  as 
they  are  very  delicate.  No  attempt  should  be  made  to  clean  them 
except  by  blowing. 

34.  The  front  and  rear  sight  brackets  (24  and  25)  and  cradle  (15) 
should  never  be  removed  from  the  carriage  unless  the  carriage  is 
to  be  dismounted.  When  not  in  use,  these  parts  should  be  kept 
covered  by  hoods  provided  for  the  purpose.  All  bright  parts  should 
be  kept  thoroughly  oiled,  special  care  being  given  to  the  deflectiou 
Worm  box  (8),  sight  shank  (23),  and  the  steel  bearings  in  the  cradle 
for  the  telescope.  Care  should  be  taken  not  to  remove  the  oil  when 
putting  on  the  hood.  The  oil  should  be  wiped  off  before  use.  The 
hood  should  be  removed,  and  the  sights,  brackets,  cradle,  etc.,  ex- 
amined at  least  once  in  every  two  weeks,  and  the  cradle  (15)  should 
be  moved  in  elevation  and  deflection,  so  that  as  much  as  possible 
of  the  sight  shank  (23)  and  deflection  worm  box  (8)  can  be  inspected. 
No  oil  should  be  allowed  on  the  surfaces  of  the  lenses  and  prisms. 

35.  Special  care  should  be  taken  in  the  use  of  the  two  small  elec- 
tric lamps  (E9J)  and  (E9H),  as  they  are  fragile.     Each  lamp  should 

seat  in  its  receptacle  not  less  than  1§  turns. 

« 

DISMANTLING  AND  ASSEMBLING. 

36.  General  instructions  for  disassembling  and  cleaning  are  given 
in  pamphlet  No.  1795,  Instructions  for  the  Care,  Preservation,  Re- 
pair, and  Adjustment  of  Instruments  for  the  Fire  Control  Systems 
for  Coast  and  Field  Artillery,  paragraphs  24  to  28,  and  35  to  38,  in- 
clusive. 

37.  If  a  sight  is  packed  for  shipment,  special  attention  should  be 
given  to  the  blocking  of  it  in  its  packing  box  to  prevent  all  move- 
ment of  the  sight  during  transit.  The  telescope  should  be  packed 
separately. 

38.  When  ordering  spare  parts,  use  the  following  nomenclature. 


14 


NOMENCLATURE  OF  PARTS.    (Plates  I  and  II.) 


No.  on 
[plates. 

Piece  marks. 

Name  of  part. 

2S9J 

Side  window. 

2S9H 

Top  window. 
Prism-cover  screw. 
Prism-holder  screw. 

EA18J 

2S2A 

EA18J 

Lamp-bracket  screw. 
Cross- wire  holder  screw. 

EA18E 

9 

EA18D 

EA18F 

2S2J 

Focusing-nut  screw. 

Finger-grip  screw. 

Tube  (for  sights  1  to 45,  inclusive). 

Tube  (sights  46  and  following  numbers  only). 

Prism  holder  (sights  1  to  45,  inclusive). 

Prism  holder  (sights  46  and  following  numbers  only. 

Amber-glass  holder  screw. 

9 

2S2LB 

53 

2S2L 

53 

EAllN 

2S2M 

EAim 

EA18C 

EAllQ 

Tube  plug. 
Chain  screw. 
Prism  spring. 
Amber-glass  disk. 

2S9D 

EA18B 

Cross-wire  screw. 

2S2ZA 

Amber-glass  holder  pin. 

Objective. 

Prism. 

Prism. 

49 

EAllG 

48 

JEAllJ 

[EAllK 

45 

42 

6 

EAllL 

EAllM 

EA18A 

Field  lens. 

Eye  lens. 

Prism  cover  (sights  46  and  following  numbers  only). 

EA18H... 

Focusing-sleeve  set  screw.               - 
Objective  separator. 
Peep  sight. 

4 

EAllH 

2S3A 

55 

2S3B       .   . 

Peep-sight  screw. 
Front-sight  holder. 

16 

2S3C 

15 

2S3D 

Cradle. 

19 

2S3E 

Deflection  scale  pointer. 
Deflection  scale  pointer  screw. 
Cover. 

2S3F 

2S3G 

2S3FA     . .     . 

Clamping  screw. 

2S3GA....    . 

Clamping  screw. 

2S3K 

Cover  screw. 

2S3L 

Front  sight  screw. 

2S3M 

Front  sight  ring. 
Telescope  clamp  (front). 

12 

2S3N 

15 

NOMENCIiATURE  OF  PARTS.    (Plates  I  and  II.)— Continued. 


No.  on 
plates. 

Piece  marks. 

Name  of  part.                                    ' 

2S2RB 

Objective  locking  ring  screw. 

2S2QB 

Objective  cell  locking  screw. 

2S2PB 

Eye  lens  cell  locking  screw. 

2S2HA 

Lock  washers. 

2S3P 

Cradle  liner. 

2S3Q 

Front  sight  bar. 

Telescope  clamp  (rear). 

Sight  bracket  and  cradle  number  plate. 

Elevation  scale. 

5 

2S3R 

2S8J....^ 

33 

2S3T 

23 

2S3V 

Sight  shank. 

2S3W    .   . 

Clamp  pin. 
Worm  bushing. 
Deflection  worm. 

2S3X     . 

40 

2S3Y 

2S3Z.        .   . 

Worm  nut. 

7 

2S3AA-  .     .   . 

Worm  knob. 

38 

2S3BA    .     .   . 

Deflection  scale. 

2S3CA 

Stop  screw. 
Sight-shank  stop. 
Cradle-liner  rivet. 

2S3DA 

2S3EA 

20 

2S4A 

Fulcrum. 

2S4B 

Elevating  worm  gear. 
Elevating  wheel  handle. 
Elevating  wheel-handle  stem. 

2S4C 

2S4D 

2S4E 

Elevating  wheel  nut. 

21 

2S4F 

Elevating  wheel. 

29 

2S4G 

Range  drum. 

2S4H 

Range-drum  scale. 

2S4J 

Si>ring  stu(L 

Elevating  worm  bushing  (front). 

Range-pointer  screw. 

Elevating  gear  spring. 

Range  pointer. 

Range-drum  washer. 

Elevating  worm  bushing  (rear). 

Elevating  worm. 

Elevating  worm-gear  shaft. 

Spanner  wrench. 

Oil  screw 

2S4K 

2S4L 

2S4M 

52 

2S4N '..... 

56 

2S4P 

2S4Q 

36 

2S4R 

39 

2S4S 

2S4T 

2S8M. 

18 

2S8K 

Front-sight-bracket  cap. 
Front-sight-bracket  cap  bolts. 

2S8L 

16 


NOMENCLATURE  OF  PARTS.     (Plates  I  and  II.)— Continued. 


No.  on 
plates. 

Piece  marks. 

Name  of  part. 

2S8H 

Sight-shank  liner. 

2S8E 

Elevation  pointer. 

2S8D            .   .. 

Front-sight  bracket  bolt. 

24 

2S8C 

Front-sight  bracket. 

2S8B 

Rear-sight-bracket  bolts. 

25 

2S8A 

Rear-sight  bracket. 

30 

2S8F 

Gear-case  cover. 

2S8G            .   . 

Gear-case  cover  bolts. 

13 

EA17A 

Objective  shutter. 
Objective-shutter  handle. 

22 

EA17B 

EA17D 

EA17C 

Objective-shutter  spring. 
Objective-shutter  shaft. 
Objective-shutter  plunger. 

EA17G 

EA17E 

Objective  cell. 
Objective  ring. 
Focusing-sleeve-nut  wrench. 

EA17F 

EA17H 

44 

EA17J 

Focusing  sleeve. 

3 

EA17K 

Focusing  ring. 

37 
50 

EA17L 

EA17M 

Focusing-sleeve  nut.  , 
Draw  tube. 

EA17N 

EA12H 

Focusing  nut. 
Cross-wire  clip. 

47 
46 

EA17P 

EA17Q 

Cross  wires. 
Cross-wire  holder. 

43 
2 

EA17R 

2S9A 

Eyepiece  tube. 
Eyepiece  dial. 
Eyelens  cell. 
Spring  washer. 
Amber  glass  holder. 

2S9B 

2S9C 

41 

2S9E 

54 

2S9F    

Eyepiece  cover. 
Rubber  hood. 

1 

2S9G 

11 

EA17S 

EA17T 

EA17U 

EA17W 

EA17V 

Lamp  bracket. 

Lamp-bracket  diaphragm. 

Lamp-bracket  bushing. 

Platinum  mirror. 

Finger  grip. 

Mirror  holder.                                                                      / 

EA17X 

31 

EA17Y 

EA12F 

EA18G 

Lamp-bracket  cap. 

Chain. 

Focusing-sleeve-nut  set  screw. 

17 

NOMENCLATURE  OF  PARTS.     (Plates  I  and  II.)— Continued. 


No.  on 
plates. 


32&28 

14 
26 


8 

10 
17 
34 
51 


Piece  marks. 


E9B 

E9J  or  E9H 

2S3EA 

2S3LA 


Name  of  part. 


Lamp  holders. 

Electric  lamp. 

Conduit  clamp. 

Lighting  cables. 

Clamping  wing  nut. 

Clamping  wing  nut. 

Bo  wen  oilers  No.  "2A." 

Spring  cover  No.  1. 

Deflection  worm  box  and  head  of  sight  shank. 

Elevating  rack. 

Front  sight. 

Lamp  hocusing  for  range  drum  and  elevation  scale. 

Diaphragms. 


War  Department, 

Office  of  the  Chief  of  Ordnance, 

Washington,  March  1,  1917. 
October  11,  1907. 
Revised  October  11,  1910. 
Revised  December  10,  1913. 
Revised  Marel>l,  1917. 
Form  No.  1956 
Ed.  Mar.  1-17—500. 


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